Ring connector for implantable medical devices

ABSTRACT

An electrical contact for use in the header assembly of an implantable tissue stimulator includes a metal housing having a base and a sidewall where the opening in the base is adapted to receive the terminal of a medical lead therethrough. An electrical contact support member is welded to the edge of the sidewall and affixed to the support member are a plurality of spring members that are tangent to an imaginary circle whose diameter is slightly less than the outside diameter of the lead terminal contact rings. When the contacts are axially aligned in the device header, the terminal of an electrical lead may be longitudinally inserted into the header to establish electrical contact with device feedthrough wires that are joined to the electrical contacts in the header.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/190,591, filed Jul. 27, 2005, which is a continuation of applicationSer. No. 10/374,037, filed Feb. 25, 2003, now U.S. Pat. No. 7,003,351,the specifications of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention relates generally to implantable electronic tissuestimulating apparatus of the type including a pulse generator that iscoupled through a medical lead to target tissue, and more particularlyto the design of electrical contacts used in a header of such a pulsegenerator to mechanically and electrically couple the pulse generator'sinput/output pins to a proximal terminal of a medical lead.

II. Discussion of the Prior Art

Over the past 30 years great strides have been made in increasing thefunctional performance of and decreasing the physical size ofimplantable medical devices, such as those designed for cardiac rhythmmanagement and neural stimulation. Generally speaking, currentstate-of-the-art implantable medical tissue stimulating devicesincorporate a battery power supply and a microprocessor-based controllerthat is designed to control a pulse generator, causing it to issuepulses at times determined by the microprocessor-based controller. Thepulses are conveyed to target tissue on or in the heart by means of oneor more medical leads having sensing/stimulating electrodes at a distalend and the electrodes are connected by lead conductors to electricalcontacts on a connector pin located at the proximal end of the lead. Thelead connector connects the lead to the pulse generator.

While a variety of lead connectors have been devised, a majorimprovement in lead connectors has been the low profile, in-line bipolardesign. An in-line connector places both electrical terminals on asingle lead pin, with an insulating barrier separating the anode contactfrom the cathode contact. To facilitate compatibility between pulsegenerators and leads of differing manufacturers, standards have beendeveloped. More particularly, a collaborative effort between IEC andInternational Standards Organization has defined the parameters of alow-profile connector referred to as IS-1 for unipolar and bipolar leadsand DF-1 for defibrillator leads. Additionally, there is ongoing work todevelop AAMI and potentially ISO standards for connectors for tripolarand quadrapolar leads.

As those skilled in the art appreciate, the lead connector must bemechanically and electrically secured to the implantable device in a waythat remains secure following implantation, but which can be readilydetached if and when it becomes necessary to install a new pulsegenerator. The Persuitti et al. U.S. Pat. No. 6,044,302 describes aconnector port for an implantable pulse generator that can accommodate aplurality of in-line lead terminal pin having multiple contacts. In the'302 patent, a lead port has one or more connector blocks each includinga set screw to lock the lead connector in contact with the connectorblock. The connector blocks are, in turn, connected to a feed-throughwire. A single elastomeric seal is provided within the port such thatwhen the connector pin is inserted therethrough, it precludes ingress ofbody fluids into the bore in the header. It is also known in the art toprovide sealing rings on the lead terminal connector itself for creatinga fluid impervious seal upon insertion of the lead's terminal into aconnector port. In this regard, reference is made to the Hawkins et al.U.S. Pat. No. 6,029,089.

Copending application Ser. No. 10/222,151 filed on Aug. 16, 2002, andentitled “Connector Port Construction Technique for Implantable MedicalDevice”, now U.S. Pat. No. 7,047,077, which application is assigned tothe assignee of the present application, there is described a connectorport for an implantable medical device that is capable of accommodatingmultiple feedthrough wires and lead connector contacts and that is smallin size, easy to assembly and which exhibits a low insertion force. Thelead connector contacts described in the aforereferenced application(referred to herein as a toroidal spring design) comprise a metalhousing having a circular bore formed through the thickness dimensionthereof. The wall defining the bore includes an annular recess forcontaining a canted-coil spring that is formed as a ring. A number ofsuch electrical contacts are concentrically aligned in a molded plasticheader with elastomeric seals disposed between each such contact. Afeedthrough wire on the pulse generator is then welded to the housingcontaining the canted-coil spring. Upon insertion of a lead terminal,the spring is spread to receive a terminal contact therein and the coilspring engages the terminal contact at a multiplicity of points aroundits circumference.

The use of the currently available spring design is not optimal. Thetoroidal spring “floats” within the bore of the housing comprising thecontact and makes connection between the terminal and spring, and inturn, between the spring and contact housing only through physicalinterference. This can lead to an unnecessarily high resistanceconnection between the connector contact member and the contacts on thelead's terminal pin. Other spring designs for this application are toolarge to fit within the required space or also float within theirhousing.

It is accordingly a principal object of the present invention to providea small, improved, cost effective connector contact for use in theheader of an implantable pulse generator and which provides a morepositive connection between a feedthrough wire of the pulse generatorand a lead terminal.

SUMMARY OF THE INVENTION

The present invention provides an electrical connector contact for usein the header assembly of an implantable cardiac rhythm managementdevice for mating with a terminal pin of a tissue stimulating/sensinglead. The contact connector comprises a metal housing that has a baseand a sidewall. A central opening in the base is sized to receive aterminal pin of a medical lead therethrough with a predeterminednon-contact clearance. A plurality of spring members are attached to anelectrical contact support member where the support member has anoutside shape permitting placement on an exposed edge of the sidewall ofthe housing. The spring members are attached to the contact supportmember such that they project inwardly of the inside opening of theelectrical contact support member to provide an interference fit with alead terminal pin that is inserted through the opening in the base ofthe housing and through the electrical contact support member.

In one embodiment, the spring members are generally shaped to provide aninterference fit with minimal drag, allowing compression thereof whenthe terminal pin of the tissue stimulating lead is inserted. In analternative embodiment, the electrical contacts are bent cylindricalbars having one end welded to the contact support member and a straightsection oriented tangent to a circle that is centered with respect tothe opening in the base and of a lesser diameter than the opening in thebase.

DESCRIPTION OF THE DRAWINGS

The foregoing features, objects and advantages of the present inventionwill become apparent to those skilled in the art from the followingdetailed description of a preferred embodiment, especially whenconsidered in conjunction with the accompanying drawings in which:

FIG. 1 is an isometric view of a ring connector comprising a firstpreferred embodiment;

FIG. 2 is a cross-sectional view taken along the line 2-2 in FIG. 1;

FIG. 3 is a cross-sectional view taken along the line 3-3 in FIG. 2;

FIG. 4 is an isometric view of a contact ring used in the assembly ofthe embodiment of FIG. 1;

FIG. 5 is a cross-sectional view along the line 5-5 in FIG. 4;

FIG. 6 is an isometric view of an alternative preferred embodiment ofthe invention;

FIG. 7 is a cross-sectional view taken along the line 7-7 in FIG. 6;

FIG. 8 is a cross-sectional view taken along the line 8-8 in FIG. 7; and

FIG. 9 is an isometric view of one of the contacts used in theembodiment of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is shown a ring connector for use in theheader of an implantable tissue stimulator, such as a cardiac pacemakeror an automatic implantable cardiac defibrillator. The ring connectormay be used in the manner fully described in the aforereferencedco-pending application Ser. No. 10/222,151, now U.S. Pat. No. 7,047,077,which is hereby incorporated by reference. It is seen to comprise ahousing member 12 made of a suitable metal. It had a base 14 and asidewall 16, where the base 14 includes an opening 18 that is of apredetermined size slightly larger than the diameter of a lead terminalthat is to be inserted therethrough. As a result, there is apredetermined non-contact clearance between the opening and the leadterminal. Resting atop the exposed edge 20 of the metal contact housing12 is a washer-like plate 22 that is welded to the exposed edge 20 ofthe housing. The central opening 24 of the washer 22 is generally sizedsuch that a lead terminal will also have a non-contact clearance withthe washer 22.

As seen in the cross-sectional view of FIG. 2, a spring contact member26 is welded to the washer 22. Referring momentarily to FIG. 4, thespring contact member 26 is made of a suitable metal, such as MP35N. Ina preferred form, the contact members are formed with the ring 28 in astamping and bending operation.

The cross-sectional view of FIG. 5 shows that the contacts 30 of themember 26 are generally shaped to provide interference with minimaldrag, having a straight back portion 32 that is generally perpendicularof the plane of the ring 28 and an arcuate front portion 34. Thecurvature of the front portion 34 is such that it is tangent to animaginary circle that is of a lesser diameter than the opening in member28 and the openings 18 and 24 seen in FIG. 1.

Referring next to the cross-sectional view of FIG. 3, it can be seenthat the contact member 26 of FIG. 4 is welded at points represented bythe black dots 38 in the drawing to the washer 22 and that the contacts30 encroach into the opening defined by the aperture of the contactsupport member 26. The tolerances are such that when a lead terminal isinserted through the opening 18 in the housing member 12 with apredetermined force, it will deflect the springs 30 which thenintimately engage a contact ring on the lead terminal to establishelectrical contact at a multiplicity of points, resulting in a lowimpedance connection.

While the embodiment described illustrates six contacts 30 on the springcontact member 26, a greater or a fewer number of such contacts may beutilized. As a minimum, however, there should be at least three suchcontacts, but with six such contacts being preferred. The contacts 30will be deflected as the lead terminal is inserted through the ringconnector 10. While the embodiment reflected in FIGS. 1-5 show thecontact ring 28 spot-welded to the underside of washer 22, it is alsopossible to insert the contact ring 28 into the housing with thecontacts 30 projecting upward from the base 14.

FIGS. 6-9 illustrate an alternative embodiment of the ring connector ofthe present invention. The ring connector, indicated generally bynumeral 40, again comprises a metal contact housing 42 having a sidewall44 supported on a base 46. The base has an opening 48 formedtherethrough that is sized to receive a lead terminal with non-contactclearance. Again, the size of the opening 48 is slightly greater thanthe diameter of a ring contact on a medical lead to be inserted throughthat aperture. The aperture 48 is preferably beveled, as at 50, tofacilitate or guide the insertion of a lead's terminal therethrough.Welded to an exposed edge 52 of the wall 44 is a contact plate 54 in theform of a washer having an opening 56 that is seized to receive a leadterminal with non-contact clearance. At regular intervals, e.g., every60°, a small hole, as at 58, is drilled through the contact supportmember 54. Fitted into each of these holes is one end 60 of a generallybent cylinder contact 62. An isometric view of one such bent cylindercontact is shown in FIG. 9.

Referring to FIG. 8, before being welded in place within the holes 58,the contacts 62 are aligned in a manufacturing jig (not shown) so thatthe straight section 66 of the bent cylinder is tangent to an imaginarycircle represented by the broken line 68 in FIG. 8 and bent end portion64 is directed away from that circle. When a lead terminal is insertedthrough the contact member assembly 40, the cylindrical bar contact 62will be deflected so as to press against a contact surface of the lead'sterminal to establish a low resistance path between the pulse generator(not shown) that attaches to the housing 42 and the aforesaid leadcontact surface.

When the ring contact assemblies 10 and 40 of FIG. 1 or FIG. 6,respectively, are axially aligned in the header of an implantablemedical device of the type concerned here, they electrically couple thedevice's high or low voltage output to a corresponding medical leadterminal. No outside mechanical actuation or tools are required, such asset screws or Allen wenches. In addition, the contact assemblies of thepresent invention are less costly than known prior art ring contactarrangements.

The physical geometry of the contacts disclosed herein is quitedifferent from known prior art approaches. The spring tabs or bentcylinders of the present invention, instead of the canted toroidalsprings of the prior art, yield improved results. The prior artcompetitive contact has an inherent disadvantage in that its toroidalspring “floats” within the housing and makes connection between theterminal and housing only through physical interference. The contactsdisclosed in the present application are solidly connected (i.e.,welded) to the housing, thus improving the electrical quality of theconnection.

This invention has been described herein in considerable detail in orderto comply with the patent statutes and to provide those skilled in theart with the information needed to apply the novel principles and toconstruct and use such specialized components as are required. However,it is to be understood that the invention can be carried out byspecifically different equipment and devices, and that variousmodifications, both as to the equipment and operating procedures, can beaccomplished without departing from the scope of the invention itself.

1. A connector for use in an implantable medical device to mate a leadterminal of an implantable lead, the connector comprising: a housingincluding a base, an exposed edge, a sidewall coupled between the baseand the exposed edge, and a housing opening sized to receive the leadterminal; a plate welded to the exposed edge and including a plateopening sized to receive the lead terminal; and a plurality of springcontacts affixed to the plate and tangent to an imaginary circle, thespring contacts each including a portion tangent to the imaginary circleand deflected to press against the lead terminal when the lead terminalin inserted through the housing opening and the plate opening.
 2. Theconnector of claim 1, wherein the housing opening is sized to receivethe lead terminal without contacting the lead terminal.
 3. The connectorof claim 1, wherein the plate opening is sized to receive the leadterminal without contacting the lead terminal.
 4. The connector of claim1, comprising a spring contact member including the plurality of springcontacts and a ring connected to the plurality of spring contacts, thering including a ring opening and welded to the plate.
 5. The connectorof claim 4, wherein the imaginary circle is smaller than the housingopening, the plate opening, and the ring opening.
 6. The connector ofclaim 5, wherein each spring contact of the plurality of spring contactscomprises: a straight back portion connected to the ring and generallyperpendicular to the plate; and an arcuate front portion connected tothe straight back portion and having a curvature tangent to theimaginary circle.
 7. The connector of claim 6, wherein the springcontact member is made of MP35N.
 8. The connector of claim 6, whereinthe spring contact member is formed by stamping and bending.
 9. Theconnector of claim 1, wherein the plurality of spring contacts comprisesa plurality of bent cylinder contacts configured to contact the leadterminal, each bent cylinder contact of the plurality of bent cylindercontacts including a first end affixed to the plate, a straight sectiontangent to the imaginary circle, and a bent end portion directed awayfrom the imaginary circle.
 10. The connector of claim 9, wherein theplate comprises a plurality of holes, and the first ends of theplurality of bent cylinder contacts are each fitted into a hole of theplurality of holes.
 11. A method for connecting an implantable lead toan implantable medical device, the method comprising: providing ahousing in the implantable medical device, the housing including a base,an exposed edge, a sidewall coupled between the base and the exposededge, and a housing opening in the base; welding a plate to the exposededge of the housing, the plate including a plate opening; and affixing aplurality of spring contacts to the plate, the plurality of springcontacts pressing against a lead terminal of the implantable lead whenthe lead terminal is inserted through the housing opening and the plateopening.
 12. The method of claim 11, wherein affixing a plurality ofspring contacts to the plate comprises affixing the plurality of springcontacts to the plate such that the spring contacts of the plurality ofspring contacts are tangent to an imaginary circle that is smaller thanthe housing opening and the plate opening.
 13. The method of claim 12,comprising sizing the opening of the housing to receive the leadterminal therethrough with a non-contact clearance.
 14. The method ofclaim 12, comprising sizing the central opening of the plate to receivethe lead terminal therethrough with a non-contact clearance.
 15. Themethod of claim 12, wherein affixing the plurality of spring contacts tothe plate comprises: providing a spring contact member including theplurality of spring contacts and a ring connected to the plurality ofspring contacts; and welding the ring to the plate.
 16. The method ofclaim 15, comprising: providing spring contacts each including: astraight back portion connected to the ring and generally perpendicularto the plate; and an arcuate front portion connected to the straightback portion and having a curvature tangent to the imaginary circle,wherein the imaginary circuit is smaller than an opening of the ring.17. The method of claim 16, wherein providing the spring contact membercomprises forming the spring contact member by stamping and bending. 18.The method of claim 17, wherein providing the spring contact membercomprises providing a spring contact member made of MP35N.
 19. Themethod of claim 12, wherein affixing the plurality of spring contacts tothe plate comprises: drilling a plurality of holes on the plate; andfitting each spring contact of the plurality of spring contacts into ahole of the plurality of holes on the plate.
 20. The method of claim 19,comprising providing the plurality of spring contacts, includingproviding a plurality of bent cylinder contacts configured to contactthe lead terminal, the bent cylinder contacts each including an endfitted into a hole of the plurality of holes on the plate, a straightsection tangent to the imaginary circle, and a bent end portion directedaway from the imaginary circle.